Hypothyroid myopathy or Hoffman's syndrome is a rare manifestation of a common condition. It's diagnosis is also difficult. We present a case of Hoffman's disease with predominant proximal myopathy and myotonia.

Hoffman Syndrome is a rare adult pseudohypertrophic myopathy associated with hypothyroidism, usually autoimmune thyroiditis. These patients present with focal or generalized muscle hypertrophy and other systemic features of hypothyroidism. [1] There have not been many cases reported in India. We report a typical case.

Muscle hypertrophy as first presentation of hypothyroidism is quite rare. [2] Our case showed predominantly myopathy with minimal systemic manifestations of hypothyroidism. There are a few cases reported in India. [2],[3] Chopra et al., noticed hypertrophy of almost all muscles of body, especially calf and arm muscles. [4] In our case, there was predominance of arm muscle hypertrophy alone.

Hoffman's disease is a specific, rare form of hypothyroid myopathy, which causes proximal weakness and pseudohypertrophy of muscles, due to connective tissue deposition. [5] Possible mechanisms for myopathy seen in hypothyroidism include an autoimmune reaction affecting the muscle, infiltration by "myxedema", or a disorder of muscle membrane. It seems most likely that thyroid deficiency affects muscle cells directly. Muscular hypertrophy with muscle stiffness in hypothyroidism is seen in less than 10% of cases. [6],[7] A serous infiltration of muscle was mentioned only in occasional case reports and was not seen in the biopsy of patient reported here. Thyroxine is well known to have important effects on cell membranes. The serum enzymes may rise to high levels in hypothyroidism, presumably because thyroid deficiency permits leakage across muscle membranes and actual muscle necrosis. [8]

A very high suspicion of hypothyroid myopathy is necessary to rule out this cause of myopathy. Patients are often misdiagnosed with myotonia, polymyositis, or muscular dystrophies. Stiffness and myoedema on percussion are not features of Duchenne and Becker muscular dystrophy, sarcoidosis, and focal myositis. Histopathology can easily distinguish these disorders. Electric silence is a point in favor of myoedema. It mimicks myotonia on percussion, but myotonic discharges are not seen on EMG.

The key point to stress is the fact that this is a treatable condition and patients with aforementioned conditions should be screened with simple thyroid profile before making the diagnosis of a more treatment resistant condition. Moreover, two or more conditions can sometimes coexist emphasizing the need for thyroid profile.

Acknowledgements

Departments of General Surgery and Pathology, Government General Hospital, Guntur.